This invention relates to a process for the explosive comminution of cellular material of animal or plant origin, in which the material is introduced into a pressure chamber, subjected to compressed gas therein, and then discharged from the pressure chamber with explosive pressure release against an impact surface.
Such a process and apparatus suitable for the performance thereof are described in U.S. Pat. No. 4,132,161. According to this document, it is known that the disintegration of the cellular material can be promoted by the material which is to be disintegrated hitting an impact surface upon pressure release and discharge.
According to the findings on which the invention is based, the impact against the impact surface imparts to the particles a mechanical impetus. Often only this starts the bursting process causing the comminution. At the beginning of the pressure release or discharge step, the particles hit the free, hard wall of the impact surface and actually receive the mechanical impetus. In the course of the pressure release or discharge step, however, a layer of comminuted particles forms on the impact surface. This causes the subsequent particles to hit this comparatively softer layer on the impact surface, so that they no longer receive a mechanical impetus which triggers the bursting process. Moreover, the subsequent particles no longer have the kinetic energy of the initially impacting particles due to continuing discharge of the pressure chamber and the consequent decrease in the pressure difference. As a result thereof, the bursting of the material particles which impact consecutively does not take place uniformly, and a material is obtained which contains coarse fractions as well as fine fractions.
However, the recovery of the components of a material is easier, the smaller the proportion of coarse fractions. Moreover, often a material with too great a variation of particle size is not wanted. Therefore, in prior art processes the coarse material was separated from the fine material, e.g., by sieving, and was recycled to explosive comminution. This causes corresponding expenses and may involve losses of valuable components. Even with repeated recycling of the coarse fraction, complete comminution of the material used cannot be achieved. This is explained by the fact that the recycled material is structurally damaged, and upon pressure release the pressure compensation takes place without a bursting process and hence without the desired comminution effect. If attempts are made to reduce the proportion of coarse material by increasing the pressure, however, there results such fine material that further processing may be made more difficult due to formation of fine dust, clogging of filters, etc.